The proposed research is a logical sequel to recent descriptive evidence challenging widely held decrement views of adult and gerontological intelligence. The focus is on examining the modifiability of adult intellectual performance. The proposed study involves a series of short-term longitudinal studies (1976-81) aimed at assessing the effectiveness of programmed intervention into the ontogeny of 240 middle-aged adults (age 50-55) and 240 elderly persons (age 65-70). In addition to two control conditions, subsamples will be randomly assigned to four treatment programs involving two aspects of intellectual functioning (Fluid Intelligence vs. Performance Set) and two follow-up maintenance programs. These intervention programs are designed within the framework of theories of adult intelligence and learning-ability relationships. The outcome will be examined with regard to treatment effectiveness, age/cohort by treatment interactions, time generalization, and transfer effects to other ability and cognitive personality dimensions. The proposed time plan is to identify the parent population and to develop or finalize measurement and intervention programs in 1976-77, to conduct the sequential longitudinal and experimental intervention project from 1978-1980, and to use the final year (1980-1981) as a period for completing the data analysis, follow-up, and report writing. BIBLIOGRAPHIC REFERENCES: Baltes, M.M., & Baltes, P.B. The ecopsychological relativity and plasticity of aging: Convergent perspectives of cohort effects and operant psychology. Zeitschrift fur Experimentelle und Angewandte Psychologie, 1977, 24, 179-197. Baltes, P. B. & Schaie, K. W. On the plasticity of intelligence in adulthood and old age: Where Horn & Donaldson fail. American Psychologist, 1976, 31, 720-725.